As has been mentioned in respect of the Swiss Pat. No. 534,913 (corresponding to U.S. Pat. No. 3,895,486), the adjustment of a quartz controlled oscillator in a timepiece is particularly complicated. If the coarse adjustment is initially effected by mechanical precision machining and thereafter by fine adjustment of the encapsulated quartz, the final adjustment is effected with the aid of a trimmer which on one hand compensates the increase of spurious capacities and on the other hand permits correcting a drift of the time base when the quartz has aged. Since the consumption of the oscillator is proportional to the square of the value of the capacities of the circuit into which it is connected, it will be understood that it is necessary to reduce such capacities as much as possible from whence there is an interest to eliminate the trimmer. Such suppression also exhibits the advantage of improving the frequency stability and of eliminating the necessity of an expensive and delicate item. The cited patent proposes on one hand to eliminate certain frequency adjustment operations for the quartz and to thus reduce its manufacturing cost while improving its stability and on the other hand to remove all electronic regulating systems (trimmer) at the stage of the time base. These purposes are attained in that the divider exhibits auxiliary electrical inputs of which the logic state determines the division relationship and in that the timepiece includes a memory coupled to these auxiliary inputs in order to retain in a coded form the information determining the division ratio by acting on these auxiliary inputs.
The system which has just been suggested necessitates the employment of a certain number of switches which provide a certain number of orders of inhibition for each adjustment period. The difficulty of obtaining these switches in a miniature form tends to limit the number thereof which in turn limits the range of possible adjustment. Furthermore, the operations of adjusting the operation are complicated and require the skills of a master watchmaker. To overcome these difficulties, the Swiss Pat. No. 570,651 (corresponding to U.S. Pat. No. 3,914,706) suggests the employment of an electronic variable memory (in place of the switches) which offers the advantage of being obtainable through the same technology as the remainder of the circuits and integrated on the same chip, to no longer limit the number of bits (enlarged field of adjustment) and of being capable of modifying the state of the memory by purely electronic operations. To achieve this purpose the last cited patent comprises a learning block which compares the period of the signal furnished to the display with an external reference which following thereon calculates the correction to be effected and which finally transfers the result into the variable memory.
In order to compare the frequency of the standard signal with the frequency provided by the timepiece oscillator, the second patent cited provides an input terminal for the standard signal, this complicating the practical production of the timepiece. To overcome this difficulty, there have already been proposed systems which do not require any auxiliary input and in which the terminals of the energy cell alone are sufficient, these being normally accessible in this type of timepiece, in order to bring about the entire adjustment of the frequency divider as well as checking this adjustment if necessary. It will be readily understood the advantages of such a system for a completely sealed wrist watch which is not readily taken apart and where only the terminals of the battery are accessible. Such type of watch is currently found on today's market and is generally formed of plastic material.
The transactions of the 59th Congress of the Societe Suisse de Chronometrie, held Oct. 4th and 5th, 1985, include a communication entitled: "A watch circuit with EEPROM for digital frequency adjustment" presented by Ronald Geddes. This communication already describes a programming system for a non-volatile memory for a timepiece where the entire programming and checking take place through the terminals alone of the energy cell. To this end, there is provided a programming circuit external to the watch and connected to the terminals of the battery and in which is stored initially a number k of pulses representing the difference in frequency between the frequency of the watch oscillator and a standard frequency. Thereafter, the voltage of the programming circuit is increased to 6.3 volts which has as effect to reset to zero the divider chain.
The number k of pulses is then introduced into this chain in lowering the energizing voltage to 5 volts k times. This accomplished, the contents of the chain is recorded into the non-volatile memory by maintaining during about 200 ms the energizing voltage at 5 volts.